1. Field of the Invention
The present invention relates generally to data communications systems and, more particularly to, a system and packet data frame for transferring a data signal in a contiguous sequence over a channel.
2. Prior Art
Typically, a data signal is transmitted over a channel in a fixed length data packet. The source of the data signal, typically a sensor, is generally allocated to a fixed slot or port, and communication systems are limited by the number and types of sensors that can be used. The addition of a sensor generally requires reconfiguring the hardware of the system.
The size of a channel, or the amount of information that can be transmitted over the channel in one packet is also limited. The typical data signal is broken down into a variable number of fixed size data packets, each having its own header and identifier. The data packets are transmitted over the link and must be reorganized and reassembled into the original message on the receiving side. For example, U.S. Pat. No. 5,870,394 to Oprea discloses a method and apparatus for the reassembly of data packets into messages. In Oprea, messages are defined into a plurality of data packets having respective header and payload portions. The header portion includes information related to the channel associated with the data packet and whether or not the data packet is the final data packet in the message. The reassembly processor must reassemble the different data packets from different channels into a contiguous message format.
The present invention is directed to, in a first aspect, a packet data frame comprising a data signal and a header appended to the data signal. The header includes information corresponding to a length of the data signal that is used by the data communication system to transmit and receive the data signal in a contiguous sequence.
In another aspect, the present invention is directed to a system for transferring a data signal over a channel. The system comprises a first data transfer device and a second transfer device coupled by a channel. The first data transfer device is adapted to append a header to a data signal and transmit the header and data signal over the channel. The header includes information corresponding to a length of the data signal that is used by the system to transmit and receive the data signal in a contiguous sequence. The second data transfer device is adapted to receive the header and data signal. The second data transfer device is also adapted to use the information corresponding to the length of the data signal to receive the data signal aligned in the same contiguous sequence as it was transmitted.